The vast majority of night vision devices have a monochromatic output. They typically work by using a lens to focus light from a scene onto the front of a sensor or image intensifier tube. The image is amplified and finally output on a phosphor display screen. While night vision (NV) is itself a great enhancement of normal human vision, it is sometimes desirable to have a NV device with a full-color output, for example to better differentiate an object one is searching for from its background environment.
At present, most typical methods of achieving a full-color NV device have been by the use of an especially sensitive and highly amplified CCD device (television camera). Alternatively, three separate image intensifier tubes are used that are selected or filtered so as to be sensitive to the red, green and blue portions of the spectrum. The outputs of these three tubes are then fused by the use of partially silvered prisms or mirrors or by integrating them in an interlaced red, green and blue (RGB) television-type display tube.
Among the disadvantages of these techniques are higher power usage, added weight, increased optical complexity compared to a simple image intensifier NV device, and susceptibility to being knocked out of alignment. In addition, CCD devices are not effective image intensifiers and thus limit the light amplification possible. Also many night vision devices are designed so as to be mounted on the user's head, a position where excess weight can be a problem. In addition, there is a vast installed base of monochromatic NV systems. Also, such techniques generally try and recreate the full color image by filtering light into three (3) optical channels (i.e., red, green and blue light).
There is described in International Application No. PCT/US01/05866 and U.S. Pat. No. 6,614,606, which are owned by the assignee of the present invention and whose teachings are incorporated herein by reference, methods of converting monochromatic night vision or other electro-optical viewing devices to portray a full-color image. The techniques and/or methods described therein yield night vision devices or other electrode-optical viewing devices that convert a monochromatic image so as to portray a full-color image and that avoid prior art shortcomings of higher power usage and increased optical complexity. The described methods or techniques, while advancing the art as to conversion of such monochromatic images to full color images, do not describe all particular techniques for designing filter systems or sub-systems for such use.
It thus would be desirable to provide two optical channel filtering systems or sub-systems that can provide color output from monochromatic-output electro-optical systems as well as devices; apparatuses and methods that embody such filtering systems. It would be particularly desirable to provide such filtering systems or sub-systems as well as related apparatuses, devices and methods, that would be adaptable to use any of a number of types of filters or filtering arrangements to provide the color output from the monochromatic output of electro-optical systems using a two channel filtering technique. It also would be highly desirable to provide a simple and low-cost technique whereby an apparatus; device or system embodying a monochromatic-output NV system is capable of providing a full-color output.